S
M
T
W
T
F
S
30
77°
66°
31
81°
68°
1
82°
68°
2
82°
67°
3
81°
61°
4
81°
60°
5
75°
61°
6
75°
66°
7
76°
66°
8
79°
65°
9
80°
66°
10
77°
65°
11
79°
64°
12
80°
65°
13
78°
65°
14
78°
64°
15
79°
65°
16
80°
61°
17
77°
64°
18
75°
60°
19
76°
57°
20
71°
55°
21
70°
54°
22
69°
60°
23
69°
58°
24
74°
54°
25
68°
53°
26
67°
52°
27
69°
55°
28
73°
59°
29
72°
55°
30
73°
54°
1
67°
57°
2
67°
50°
3
70°
50°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Stony Brook
Stony Brook's September 2026 forecast shows daily high temperatures ranging from 67° to 82°, with overnight lows between 50° and 68°. The average high for September is 75° with an average low of 60°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in Stony Brook. See also: October | November | December.
